1. Field of the Invention
The present invention is directed to the steroidal alkaloid glycosyl transferase enzyme β-solanine/β-chaconine rhamnosyltransferase (SGT3) which is involved in the biosynthesis of steroidal glycoalkaloids in Solanaceous plants. More particularly, the invention is directed to nucleic acid sequences that encode SGT3, recombinant polynucleotide molecules containing the sequences, and uses thereof. A particular use of the nucleic acid sequences and portions thereof is to inhibit SGT3 activity and reduce the levels of the steroidal glycoalkaloids α-chaconine and α-solanine in Solanaceous plants.
2. Description of the Art
Solanaceous plants include such agronomically important crops as potato, tomato and eggplant. Many Solanaceous species, including potato, synthesize bitter tasting steroidal glycoalkaloids (nitrogen-containing steroidal glycosides) as a defense against microbial or insect pests or in response to environmental stress. Accumulation of these natural toxicants can affect food quality and safety, especially in improperly stored or processed potatoes. This has led to the implementation of a guidelines limiting glycoalkaloid content in a tuber of a given potato cultivar to 20 mg/100 gm. While the guidelines provide effective protection for the consumer, its effectiveness is dependent upon limiting the release of new cultivars for commercial production to those with acceptable glycoalkaloid levels. For potato breeding programs to develop new cultivars with improved agronomic or processing properties, the need to select also for low levels of glycoalkaloids can present a difficult problem. A method to decrease the glycoalkaloid content of any newly developed cultivar with minimum impact on other characteristics would be of great use to obtain valuable new commercial potato cultivars.